VEHICLE STARTED FEELING SLUGGISH, REPAIR FACILITY CHANGED SPARK PLUGS, AN IGNITION COIL, AND A HALL SENSOR. FACILITY ADMITTED THEY COULD NOT REPAIR VEHICLE SO IT WAS DRIVEN TO A DEALER FOR DIAGNOSIS. WHILE BEING DRIVEN TO THE DEALER, THE VEHICLE STARTED SMOKING. CONTINUED DRIVING, ARRIVED AT DEALER, AND THERE WAS A FIRE UNDER HOOD. EXHAUST SYSTEM OVERHEATED, BURNING MATERIALS ON THE RIGHT FRONT FLOORBOARD. *NM